If you want good Boss damage and aren't use to sneaking in casts between the interrupts then FON (and HOTW) is amazing to run with. Like someone already mentioned the Treants don't get interrupted.

However running with Incarnation+HOTW will give you amazing Bat damage as 3 Min CDs should be up as the Bats come down (CA Multi-DOTing). Overall it comes down to what your Raid needs. Personally I run with Incarnation+HOTW because the quicker the Bats die the better and we don't always have burst AOE Classes in our Raid Comp.

I always run Inc & Vigil as CA, Inc & Vigil during bats does like 8million healing. Surpassing any hotw tranq and doesn't require a bop. I end up doing 12 - 15million healing from Vigil on our kills.
HoTW prolly has less value due to not being able to free cast and limited boss uptime during kite phase.

Try getting a tranq out past 4 stacks without UR. On the other hand, the debuff is pretty much a nonissue on 25, so i have little use for that.

I haven't try it, I did it. Multiple time. At arround 14+ stacks. You just need a devo aura or a BoP. Like I said, if your group needs the DPS, go for UR. If your group needs more healing/dispell, go for Mass Dispell. Will save mana and a GCD to your healers.

Damn not that many comments in i saw i had made mistake, since i had picked Nature's vigil and treants since i thought that was better. But thanks for all the help guys, it helped me a lot to pick Incarnation and Heart of the wild instead.

Unfortunatly my guild didnt get him before raid reset. Best attempt he had 24 mil. so we will get him next week i hope.

I haven't try it, I did it. Multiple time. At arround 14+ stacks. You just need a devo aura or a BoP. Like I said, if your group needs the DPS, go for UR. If your group needs more healing/dispell, go for Mass Dispell. Will save mana and a GCD to your healers.

Beyond 4 stacks, the exact number becomes irrelevant, energy generates faster than it can be used. But you're assuming that those CDs are available in the first place, which is not always the case.